Why do my brakes vibrate more AFTER I change new pads?

CAvolvoSD · Post by **CAvolvoSD** » 08 May 2011, 19:38

I had my rear brake pads replaced 2 weeks ago at the dealer, this place used OE most of the time. I noticed the shaky feel on the pedal when I brake, is it normal after new ones are installed? Is there "break-in" period for the new pads? My brakes were fine before I changed the pads, it was thin (they told me it's 3mm). Do I need to change the rotors now? Thanks!

Post by **vjaneczko** » 08 May 2011, 19:52

Volvo dealer?

If the shake came from the brake job, go back and tell them to do it right. If you brake hard or race, you can do a bedding process for the pads, but a daily driver doesn't need it.

If they only did the pads and not the rotors, there may be an issue from this, but they should have said something about it before they gave the car back to you. There is not break-in period for pads. Did they shave the rotors? If so, they may have goofed 'em up. I prefer to buy new ones all the time, but that's me.

CAvolvoSD · Post by **CAvolvoSD** » 08 May 2011, 20:01

Yes, it is at the Volvo dealer I take my car to most service except oil changing. I don't know if they shave the rotors or not, I usually just give to them and normally they are a good service shop. I am not the demanding patron type unless I know for sure there is something wrong with the job. I 'll check with them this week. Thanks!

Post by **jimmy57** » 08 May 2011, 21:34

if it had vibration before then it will have vibration after new pads. Pads do not cause the vibration, thickness variation in the rotors causes that and pads don't fix it. Did you mention to the service advisor that it had vibration?

CAvolvoSD · Post by **CAvolvoSD** » 08 May 2011, 22:12

No, I didn't notice anything wrong with my brakes. I changed the pads due to the recommendattion they printed on the receipt last time I had my A/C service job done 1 month ago. I don't know much about car mechanical, did they have to alternate something on the rotors to put new pads on?

Post by **jblackburn** » 08 May 2011, 22:17

What sensation are you feeing exactly? Pulsing through the brake pedal is usually ABS which can be traced back to dirty wheel sensors. If the rotors are severly warped, I had a Buick that could be felt through the brake pedal as you were on the brakes.

If it's just the car kinda pulling harder for a split second, that's where your rotors are warped.

CAvolvoSD · Post by **CAvolvoSD** » 08 May 2011, 22:48

It's just pulsing, not that bad. I had warped rotors at this exact rear brake so I know what a warped rotor feel like, I had rotors replaced there 6 years ago. So you think the wheel sensor is dirty? Is it safe for the car brake or is it negligible?

mhn · Post by **mhn** » 09 May 2011, 01:06

If you had to slam on the brakes hard enough to engage the ABS a couple of times, that's enough to cut grooves in your rotors and they'll not smooth out. If your brakes vibrate *more now*, presumably they were vibrating somewhat before the job was done -- and the service provider should have caught any issues.

I'd take it back and ask the thread title of the dealer who did the pads, without volunteering anything, and see what they say. At the very least, they should offer you a discount on the labor to make it right.

instarx · Post by **instarx** » 09 May 2011, 01:45

mhn wrote:If you had to slam on the brakes hard enough to engage the ABS a couple of times, that's enough to cut grooves in your rotors and they'll not smooth out.

Do you have any references to back this statement up? I'm not necessarily saying you are wrong, but I have never heard that using the ABS a few times causes permanent damage, nor have I ever experienced it on any car I have owned.

mhn · Post by **mhn** » 09 May 2011, 02:19

instarx wrote:
mhn wrote:If you had to slam on the brakes hard enough to engage the ABS a couple of times, that's enough to cut grooves in your rotors and they'll not smooth out.
Do you have any references to back this statement up? I'm not necessarily saying you are wrong, but I have never heard that using the ABS a few times causes permanent damage, nor have I ever experienced it on any car I have owned.

No, actually, I don't. No one you'd know, anyway. I could easily be wrong and / or actual *decades* out of date, but I'd been told a couple of times by a couple of different people that making the ABS do that juddering skip it does, hard enough or more than once or twice, was enough to put ridges in the rotors. They might be subtle, but they'd possibly be enough to account for the symptom. New pads might be less acclimated to the slightly altered shape of the rotors and therefore show up the vibration a little more.

Just a thought -- one of those bits of received wisdom you don't think to question any more, but probably should. I'd still talk to the dealer.